Water Situation Report Solent and South Downs Area

Monthly water situation report Solent and South Downs Area

Summary – May 2020 Solent and South Downs (SSD) had well below average rainfall for May, receiving 11% (6mm) of the long term average (LTA) (57mm). Monthly mean river flows across SSD ranged from exceptionally low to normal. End of month groundwater levels ranged from below normal to notably high. Soil moisture deficits across Solent and South Downs ended May much higher than LTAs. End of month reservoir stocks were above average at Ardingly Reservoir (Ouse Catchment) and Arlington Reservoir (Cuckmere catchment).

Rainfall Solent and South Downs (SSD) had exceptionally low rainfall in across the entire area in May, receiving 11% (6mm) of the LTA (57mm). The Ouse areal unit in the east had the highest monthly total but still only 10mm, 18% of LTA (55mm), followed by neighbouring areal unit, Cuckmere, which had 17% (9mm) of LTA (52mm). The Lymington areal unit in the west of SSD received the lowest rainfall with 3mm (5% LTA), followed closely by the Test Chalk and Hampshire Tertiary areal units which both recorded 4mm (7% LTA). The highest daily totals for the month were recorded on the 23rd at World’s End (Hampshire Tertiaries) recording 12.2mm on one of only two days when it rained. On average, there was only one wet day over SSD, with 20 of the 68 rain gauges recording zero for the entire month.

Soil Moisture Deficit/Recharge Soil moisture deficits across Solent and South Downs ended the month greater than the long term average; more than double for the Western Rother Greensand areal unit. Soils are much drier than normal.

River Flows Monthly mean river flows across SSD ranged from notably low to above normal. The River Itchen at Allbrook & Highbridge was the only site recording above normal monthly mean flows, having the 3rd highest May monthly mean flow on record. The River Ouse at Goldbridge, the Adur at Sakeham and the Cuckmere at Cowbeech all recorded below normal monthly mean flows in May. Notably Low monthly mean flows were recorded for the Arun at Alfoldean and the Lymington at Brockenhurst, these rank as the 8th and 10th lowest May flows, respectively, on record. All other reported sites recorded normal flows.

Groundwater Levels End of month groundwater levels ranged from below normal to notably high. Preston Candover and West Meon (East Hants Chalk) levels were notably high. Clanville Gate (Test Chalk), Cornish Farm (East Sussex Chalk) and Youngwoods Copse (Isle of Wight) levels were above normal. The only site below normal was Carisbrooke Castle (Isle of Wight) which is known to respond quickly. All other sites recorded normal groundwater levels in May. Observation boreholes Harting Common and Catherington were not dipped this month due to Covid-19 restrictions. The most notable levels this month were recorded at Preston Candover and West Meon Hut which were the 3rd and 4th highest end of May levels on record.

Reservoir Storage/Water Resource Zone Stocks End of month reservoir stocks were above average at Ardingly Reservoir (Ouse Catchment) with 99.7% of total capacity (LTA 97%) and also above average at Arlington Reservoir (Cuckmere catchment) with 97% of total capacity (LTA 93%).

Environmental Impact No water resources restrictions were in operation in May. No fluvial flood alerts or warning were issued in May.

Author: HydrologySSD

All data are provisional and may be subject to revision. The views expressed in this document are not necessarily those of the Environment Agency. Its officers, servants or agents accept no liability for any loss or damage arising from the interpretation or use of the information, or reliance upon views contained herein.

www.gov.uk/environment-agency © Environment Agency 2020

Rainfall Map 1

Total rainfall for hydrological areas across Solent and South Downs for the current month, classed relative to an analysis of respective historic totals. Provisional data based on Environment Agency 1km gridded rainfall dataset derived from Environment Agency intensity rain gauges. Includes material based on Ordnance Survey 1:50 000 maps with the permission of the controller of Her Majesty’s Stationery Office © Crown copyright. All rights reserved. Environment Agency, 100026380, 2020.

www.gov.uk/environment-agency © Environment Agency 2020

Rainfall Map 2

Total rainfall for hydrological areas across Solent and South Downs for the current month (up to 31 December), the last 3 months, the last 6 months, and the last 12 months, classed relative to an analysis of respective historic totals. Final NCIC (National Climate Information Centre) data based on the Met Office 5km gridded rainfall dataset derived from rain gauges (Source: Met Office © Crown Copyright, 2020). Provisional data based on Environment Agency 1km gridded rainfall dataset derived from Environment Agency intensity rain gauges. Crown copyright. All rights reserved. Environment Agency, 100026380, 2020

www.gov.uk/environment-agency © Environment Agency 2020

River Flow and Groundwater Status Map

Underlined sites are observation wells not dipped owing to Covid-19 restrictions

Groundwater site status based on end of month level. Surface water site status based on mean monthly flow.

Some features of this map are based on digital spatial data licensed from the Centre for Ecology and Hydrology, © CEH. Includes material based on Ordnance Survey 1:50 000 maps with the permission of the controller of Her Majesty’s Stationery Office © Crown copyright. All rights reserved. Environment Agency, 100026380, 2020

Geological map reproduced with kind permission from UK Groundwater Forum, BGS © NERC

www.gov.uk/environment-agency © Environment Agency 2020

West Hampshire – Page 1

Monthly total rainfall (mm) Long term average rainfall (mm)

Test Chalk - Rainfall Lymington - Rainfall 160 160

140 140

120 120

100 100

80 80

60 60 Rainfall (mm) Rainfall Rainfall (mm) Rainfall 40 40

20 20

0 0

Jul-19 Feb-20 Jul-19 Feb-20 Jun-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Mar-20 Apr-20 May-20 Jun-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Mar-20 Apr-20 May-20

Test Chalk - Effective Rainfall Lymington - Effective Rainfall 160 160

140 140

120 120

100 100

80 80

60 60

40 40

Effective (mm) Rainfall Effective (mm) Rainfall Effective 20 20

0 0

Jul-19 Feb-20 Jul-19 Feb-20 Jun-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Mar-20 Apr-20 May-20 Jun-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Mar-20 Apr-20 May-20

RIVER TEST AT CHILBOLTON RIVER ITCHEN AT ALLBROOK GS AND HIGHBRIDGE Ranking used data from 09/01/1989 to 31/12/2017 Ranking used data from 01/10/1958 to 31/12/2017 16 14

14 12

12 10

10 8 8 6 6

Daily Flow(cumecs) Mean Daily Flow(cumecs) Mean Daily 2 2

0 0 30-Jun-19 31-Aug-19 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 30-Jun-19 31-Aug-19 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20

RIVER TEST AT BROADLANDS LYMINGTON RIVER AT BROCKENHURST Ranking used data from 01/10/1957 to 31/12/2017 Ranking used data from 01/01/1997 to 31/12/2017 35 30

30 25

25 20

20 15 15

10 Daily Flow(cumecs) Mean Daily Daily Flow(cumecs) Mean Daily 5 5

0 0 30-Jun-19 31-Aug-19 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 30-Jun-19 31-Aug-19 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data

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West Hampshire – Page 2

CLANVILLE GATE GWL - CHALK PRESTON CANDOVER GWL - CHALK Ranking derived from data for the period Mar-1963 to Dec-2012 Ranking derived from data for the period Jan-1975 to Dec-2012

94 99 92 98 90 97 88 96 86 95 84 94

82 93 Level (mAOD) Level Level (mAOD) Level 80 92 78 91 76 90 74 89 Aug-19 Dec-19 Apr-20 Aug-19 Dec-19 Apr-20

WEST MEON GWL - CHALK LOPCOMBE CORNER GWL - CHALK Ranking derived from data for the period Sep-1986 to Dec-2012 Ranking derived from data for the period Apr-1963 to Dec-2012

94 98 92 96 94 90 92 88 90 86 88 84 86 84

82 Level (mAOD) Level Level (mAOD) Level 82 80 80 78 78 76 76 Aug-19 Dec-19 Apr-20 Aug-19 Dec-19 Apr-20

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data

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East Hampshire and Isle of Wight

Monthly total rainfall (mm) Long term average rainfall (mm) East Hampshire Chalk - Rainfall Isle of Wight - Rainfall 180 160

160 140

140 120 120 100 100 80 80 60

60 Rainfall (mm) Rainfall Rainfall (mm) Rainfall 40 40

20 20

0 0

Jul-19 Feb-20 Jul-19 Feb-20 Jun-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Mar-20 Apr-20 May-20 Jun-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Mar-20 Apr-20 May-20

East Hampshire Chalk - Effective Rainfall Isle of Wight - Effective Rainfall 160 160

140 140

120 120

100 100

80 80

60 60

40 40

Effective (mm) Rainfall Effective (mm) Rainfall Effective 20 20

0 0

Jul-19 Feb-20 Jul-19 Feb-20 Jun-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Mar-20 Apr-20 May-20 Jun-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Mar-20 Apr-20 May-20

RIVER WALLINGTON AT NORTH FAREHAM RIVER MEON AT MISLINGFORD Ranking used data from 01/01/1992 to 31/12/2017 Ranking used data from 01/10/1958 to 31/12/2017 12 6.0

10 5.0

8 4.0

6 3.0

4 2.0 Daily Flow(cumecs) Mean Daily Daily Flow(cumecs) Mean Daily 2 1.0

0 0.0 30-Jun-19 31-Aug-19 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 30-Jun-19 31-Aug-19 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20

RIVER MEDINA AT BLACKWATER Ranking used data from 01/05/1989 to 31/12/2017 2.5

2.0

1.5

1.0

0.5 Daily Flow(cumecs) Mean Daily

0.0 30-Jun-19 31-Aug-19 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data

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East Hampshire and Isle of Wight – Page 2

CATHERINGTON GWL - CHALK CARISBROOKE CASTLE GWL - CHALK Ranking derived from data for the period Jan-1969 to Dec-2012 Ranking derived from data for the period Aug-1977 to Dec-2012

32 57 31 52 30

47 29

42 28 27

37 Level (mAOD) Level Level (mAOD) Level 26 32 25

27 24 Aug-19 Dec-19 Apr-20 Aug-19 Dec-19 Apr-20

YOUNGSWOOD COPSE GWL - LGS Ranking derived from data for the period Feb-1978 to Dec-2012

22 22 21 21 20 20 19

Level (mAOD) Level 19 18 18 17 Aug-19 Dec-19 Apr-20

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data

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West Sussex

Monthly total rainfall (mm) Long term average rainfall (mm) Arun - Rainfall West Sussex Chalk - Rainfall 180 180

160 160

140 140

120 120

100 100

80 80

60 60

Rainfall (mm) Rainfall (mm) Rainfall 40 40

20 20

0 0

Jul-19 Feb-20 Jul-19 Feb-20 Jun-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Mar-20 Apr-20 May-20 Jun-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Mar-20 Apr-20 May-20

Arun - Effective Rainfall West Sussex Chalk - Effective Rainfall 160 180

140 160

140 120 120 100 100 80 80 60 60 40

Effective (mm) Rainfall Effective (mm) Rainfall Effective 20 20

0 0

Jul-19 Feb-20 Jul-19 Feb-20 Jun-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Mar-20 Apr-20 May-20 Jun-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Mar-20 Apr-20 May-20

RIVER ROTHER AT IPING MILL RIVER ARUN AT ALFOLDEAN Ranking used data from 01/11/1966 to 31/12/2017 Ranking used data from 01/05/1970 to 31/12/2017 45 60

40 50 35

30 40

25 30 20

15 20

10 Daily Flow(cumecs) Mean Daily Daily Flow(cumecs) Mean Daily 10 5

0 0 30-Jun-19 31-Aug-19 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 30-Jun-19 31-Aug-19 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20

CHILGROVE HOUSE GWL - CHALK HARTING COMMON (DOWN) GWL - LGS Ranking derived from data for the period Feb-1836 to Dec-2012 Ranking derived from data for the period Jan-1984 to Dec-2012

75 101

70 101 100 65 100 60 99 55 99

50 98 Level (mAOD) Level Level (mAOD) Level 98 45 97 40 97 35 96 Aug-19 Dec-19 Apr-20 Aug-19 Dec-19 Apr-20

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data

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East Sussex

Monthly total rainfall (mm) Long term average rainfall (mm) Pevensey Levels - Rainfall Ouse - Rainfall 180 180

160 160

140 140

120 120

100 100

80 80

60 60

Rainfall (mm) Rainfall (mm) Rainfall 40 40

20 20

0 0

Jul-19 Feb-20 Jul-19 Feb-20 Jun-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Mar-20 Apr-20 May-20 Jun-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Mar-20 Apr-20 May-20

Pevensey Levels - Effective Rainfall Ouse - Effective Rainfall 180 160

160 140

140 120 120 100 100 80 80 60 60 40

Effective (mm) Rainfall Effective (mm) Rainfall Effective 20 20

0 0

Jul-19 Feb-20 Jul-19 Feb-20 Jun-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Mar-20 Apr-20 May-20 Jun-19 Aug-19 Sep-19 Oct-19 Nov-19 Dec-19 Jan-20 Mar-20 Apr-20 May-20

RIVER OUSE AT GOLDBRIDGE RIVER ADUR AT SAKEHAM Ranking used data from 01/03/1960 to 31/12/2017 Ranking used data from 01/05/1981 to 31/12/2017 60 40

35 50

40 25

30 20

15 20

10 Daily Flow(cumecs) Mean Daily Daily Flow(cumecs) Mean Daily 10 5

0 0 30-Jun-19 31-Aug-19 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20 30-Jun-19 31-Aug-19 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20

RIVER CUCKMERE AT COWBEECH Ranking used data from 01/11/1967 to 31/12/2017 8.0

7.0

6.0

5.0

4.0

3.0

2.0 Daily Flow(cumecs) Mean Daily 1.0

0.0 30-Jun-19 31-Aug-19 31-Oct-19 31-Dec-19 29-Feb-20 30-Apr-20

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data

East Sussex – Page 2

Monthly total rainfall (mm) Long term average rainfall (mm) BEEDING HILL GWL - CHALK HOUNDEAN BOTTOM GWL - CHALK Ranking derived from data for the period Sep-1979 to Dec-2012 Ranking derived from data for the period Jan-1977 to Dec-2012

75 30

73 25 71 20 69

67 15

10 Level (mAOD) Level Level (mAOD) Level 63 5 61

59 0 Aug-19 Dec-19 Apr-20 Aug-19 Dec-19 Apr-20

CORNISH FARM WIGDENS GWL - CHALK LTA MIN 2015 2018 2019 2020 Ranking derived from data for the period Mar-1981 to Dec-2012 South East Water - Ardingly Reservoir - Ouse 23 100 22

21 80 20 19 60 18 17 40

Level (mAOD) Level 16 15

14 20 Percentage of live ofcapacity Percentage live 13 Aug-19 Dec-19 Apr-20 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

LTA MIN 2015 2018 2019 2020 South East Water - Arlington Reservoir - Cuckmere 100

20 Percentage of live ofcapacity Percentage live

0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Exceptionally high Notably high Above normal Normal Below normal Notably low Exceptionally low ─── Latest data

Summary of rainfall, effective rainfall and soil moisture deficits

Rainfall and effective rainfall

LTA LTA % Effective % Rainfall effective rainfall of rainfall of Area (mm) rainfall (mm) LTA (mm) LTA (mm) Test Chalk 4 60 7% 0 10 0% East Hampshire Chalk 5 63 8% 0 12 0% West Sussex Chalk 6 60 10% 0 10 0% East Sussex Chalk 7 52 13% 0 7 2% Isle of Wight 5 54 9% 0 6 0% Western Rother Greensand 6 63 10% 0 16 1% Hampshire Tertiaries 4 58 7% 0 5 0% Lymington 3 59 5% 0 5 0% Sussex Coast 5 50 9% 0 3 0% Arun 7 60 11% 0 9 0% Adur 7 57 13% 0 8 0% Ouse 10 55 18% 0 7 0% Cuckmere 9 52 17% 0 5 0% Pevensey Levels 8 48 17% 0 3 0% Solent and South Downs 6 57 11% 0 8 0%

Summer rainfall and effective rainfall

Summer totals for the period 1 April to the 31 May 2020

LTA LTA % Effective % Rainfall effective rainfall of rainfall of Area (mm) rainfall (mm) LTA (mm) LTA (mm) Test Chalk 70 110 64% 8 25 33% East Hampshire Chalk 67 115 58% 7 28 26% West Sussex Chalk 63 120 53% 7 31 21% East Sussex Chalk 45 106 42% 4 23 18% Isle of Wight 56 104 54% 6 19 28% Western Rother Greensand 65 122 53% 7 40 17% Hampshire Tertiaries 63 106 59% 0 15 0% Lymington 55 109 51% 0 17 0% Sussex Coast 59 100 59% 0 15 0% Arun 52 116 45% 0 26 0% Adur 53 112 47% 0 24 0% Ouse 46 110 42% 0 23 0% Cuckmere 44 104 43% 0 18 0% Pevensey Levels 46 99 46% 0 14 0% Solent and South Downs 56 109 51% 3 23 12%

Soil Moisture Deficit

Area End of month SMD (mm) End of month SMD LTA (mm)

Test Chalk 84 45 East Hampshire Chalk 85 44 West Sussex Chalk 86 47 East Sussex Chalk 91 51 Isle of Wight 89 54 Western Rother Greensand 85 38 Hampshire Tertiaries 85 48 Lymington 87 47 Sussex Coast 86 51 Arun 86 46 Adur 87 47 Ouse 88 46 Cuckmere 90 49 Pevensey Levels 90 51 Solent and South Downs 87 47

Environmental Impact Flow Constraints

Forward look- river flow and groundwater September 2020

a) 120% of LTA b) 100% of LTA rainfall rainfall

Ra inf all les s th c) 80% of LTA d) 60% of LTA an rainfall rainfall 80 % LT A du rin g De c to M ar ha s oc cu rre d in 16 % to 24 % of ye ar s1 in th e Projected river flows at key indicator sites up until the end of September 2020. his Projected groundwater levels at key indicator sites at the end of September 2020. tor Projections based on four scenarios: 120% (a), 100% (b), 80% (c) and 60% (d) of ic re long term average rainfall (Source: Environment Agency). Geological map reproduced with co kind permission from UK Groundwater Forum BGS © NERC Crown copyright. All rights reserved. rd Environment Agency 100026380 2020. (si nc e 19 10 ).

Glossary Term Definition

Aquifer A geological formation able to store and transmit water.

Areal average rainfall The estimated average depth of rainfall over a defined area. Expressed in depth of water (mm).

Artesian The condition where the groundwater level is above ground surface but is prevented from rising to this level by an overlying continuous low permeability layer, such as clay.

Artesian borehole Borehole where the level of groundwater is above the top of the borehole and groundwater flows out of the borehole when unsealed.

Cumecs Cubic metres per second (m3s-1)

Effective rainfall The rainfall available to percolate into the soil or produce river flow. Expressed in depth of water (mm).

Flood Alert/Flood Warning Three levels of warnings may be issued by the Environment Agency. Flood Alerts indicate flooding is possible. Flood Warnings indicate flooding is expected. Severe Flood Warnings indicate severe flooding.

Groundwater The water found in an aquifer.

Long term average (LTA) The arithmetic mean calculated from the historic record, usually based on the period 1961-1990. However, the period used may vary by parameter being reported on (see figure captions for details).

mAOD Metres Above Ordnance Datum (mean sea level at Newlyn Cornwall).

MORECS Met Office Rainfall and Evaporation Calculation System. Met Office service providing real time calculation of evapotranspiration, soil moisture deficit and effective rainfall on a 40 x 40 km grid.

Naturalised flow River flow with the impacts of artificial influences removed. Artificial influences may include abstractions, discharges, transfers, augmentation and impoundments.

NCIC National Climate Information Centre. NCIC area monthly rainfall totals are derived using the Met Office 5 km gridded dataset, which uses rain gauge observations.

Recharge The process of increasing the water stored in the saturated zone of an aquifer. Expressed in depth of water (mm).

Reservoir gross capacity The total capacity of a reservoir.

Reservoir live capacity The capacity of the reservoir that is normally usable for storage to meet established reservoir operating requirements. This excludes any capacity not available for use (e.g. storage held back for emergency services, operating agreements or physical restrictions). May also be referred to as ‘net’ or ‘deployable’ capacity.

Soil moisture deficit (SMD) The difference between the amount of water actually in the soil and the amount of water the soil can hold. Expressed in depth of water (mm).